This invention relates generally to a cutting tool assembly having a replaceable cutting head, and more particularly to an elongated milling cutting tool assembly having a replaceable cutting head.
Such cutting tool assemblies have long been known, particularly where the replaceable cutting head has a screw bore and is secured in position by means of a clamping screw. Removing the cutting head usually involves loosening and removal of the clamping screw. Mounting a new cutting head in position then requires holding the new cutting head in position whilst inserting the clamping screw in the screw bore and tightening the clamping screw.
With such known cutting tool assemblies, handling difficulties are often encountered when removing or mounting a cutting head, especially when the cutting head is small and the clamping screw is correspondingly small.
It has been proposed in EP 0 298 937 B1, to provide a cutting tool comprising a cutting body and a shaft that supports the cutting body. The cutting body is detachably connected to a locking screw via hook-shaped means. The hooked-shaped means transfers axial forces between the cutting body and the locking screw. Both the cutting body and the locking screw are provided with hook shaped means. Both of the hooked shaped means are provided with recesses and tongues. The recesses and tongues cooperate to permanently transfer rotational movement between the cutting body and the locking means. The locking screw is provided with an externally threaded portion that is connected to an internally threaded recess provided in the shaft. The threads are designed as right hand threads for right hand cutting tools and as left hand threads for left hand cutting tools. The locking screw is movable in the axial direction by relative rotation of the externally threaded portion and the internally threaded recess. The shaft is provided with a conical seat and the cutting body is provided with a circumferential conical portion that is received in the conical seat of the shaft. The cutting body can be inserted in or removed from the conical seat by displacing the locking screw from its innermost position to an intermediate position.
The prior art cutting tool described above suffers from two basic disadvantages. First, two cutting tools of the type described above have to be provided for two cutting directions. A right hand cutting tool with right hand threads and a left hand cutting tool with left hand threads. Second, it has been found that under certain working conditions the circumferential conical portion of the cutting body becomes lodged in the conical seat of the shaft and therefore after working it is difficult to remove the cutting body from the shaft.
It is an object of the present invention to provide a cutting tool assembly that substantially overcomes the above mentioned disadvantages.
In accordance with the present invention there is provided a cutting tool assembly comprising:
a tool shank having forward end and a rear end and a longitudinal axis passing through the forward and rear ends, an elongated hole having forward and rear ends and extending axially from an opening at the forward end of the tool shank, a forward portion of the elongated hole being formed by first and second non-coaxial, partially overlapping, axially extending cylindrical bores, a threaded securing screw bore extending from a point rearward of the forward end of the tool shank in a direction transverse to the longitudinal axis of the tool shank to the second cylindrical bore;
a pull rod, generally cylindrical in shape with a longitudinal axis, the pull rod having a forward end with a forward coupling portion and a rear end with a rear recess; and
a cutting head having a forward cutting portion and a rear coupling portion cooperating with the forward coupling portion of the pull rod, the forward coupling portion of the pull rod and the rear coupling portion of the cutting head forming, when in cooperation, a joint coupling region, the pull rod and the rear coupling portion of the cutting head being retained in the elongated hole in the tool shank and secured therein by a securing screw, the securing screw being received in the threaded securing screw bore and engaging the rear recess in the rear end of the pull rod, the forward portion of the elongated hole and the joint coupling region having substantially the same cross sectional forms.
In accordance with a preferred embodiment of the present invention, the rear coupling portion of the cutting head is generally cylindrical in shape having a longitudinal axis and a recess having a generally axially extending planar coupling surface transversely directed with respect to the longitudinal axis of the cutting head.
Further in accordance with a preferred embodiment of the present invention, the forward coupling portion of the pull rod has a forward recess with a generally axially extending planar coupling surface transversely directed with respect to the longitudinal axis of the pull rod.
In accordance with the present invention, the coupling surface of the cutting head abuts the coupling surface of the pull rod.
In accordance with a preferred embodiment, the pull rod is provided with an intermediate recess between the forward recess and the rear recess.
Further in accordance with a preferred embodiment, an elongated indentation is formed in the pull rod, the elongated indentation extending between the intermediate and rear recesses in the pull rod, the elongated recess having a substantially planar guide surface.
Yet further in accordance with a preferred embodiment, the tool shank is provided with a second threaded bore and a guide screw, the second threaded bore being substantially perpendicular to the longitudinal axis of the tool shank and extending to the second cylindrical bore, the second threaded bore capable of receiving the guide screw, the guide screw having a threaded portion and a screw head and a front end axially remote from the screw head, the second threaded bore being adjacent the threaded securing screw bore, the arrangement being that in an assembled cutting tool assembly, the screw head of the guide screw is adjacent to but not in contact with a rear end of the securing screw and the front end of the guide screw is adjacent to but not in contact with the guide surface.
Preferably, the threaded securing screw bore and the second threaded bore open out to a joint aperture in the tool shank.
Preferably, the cutting tool assembly is provided with a spring located between the rear end of the pull rod and the rear end of the elongated hole.
If desired the tool shank is provided with a side aperture enabling contact to be made with the pull bar through the side aperture.
There is also provided in accordance with the present invention, a method for assembling a cutting tool assembly comprising an initial assembling procedure followed by a final assembling procedure;
the initial assembling procedure comprising the steps of:
(a1) providing a tool shank having forward end and a rear end and a longitudinal axis passing through the forward and rear ends, an elongated hole having forward and rear ends and extending axially from an opening at the forward end of the tool shank, a forward portion of the elongated hole being formed by first and second non-coaxial, partially overlapping, axially extending cylindrical bores, a threaded securing screw bore extending from a point rearward of the forward end of the tool shank in a direction transverse to the longitudinal axis of the tool shank to the second cylindrical bore and a second threaded bore adjacent the threaded securing screw bore, the second threaded bore being substantially perpendicular to the longitudinal axis of the tool shank, the threaded securing screw bore and the second threaded bore opening out to a joint aperture in the tool shank;
(b1) providing a pull rod, generally cylindrical in shape with a longitudinal axis, having a forward end with a forward coupling portion and a rear end with a rear recess, the forward coupling portion of the pull rod having a forward recess with a generally axially extending planar coupling surface transversely directed with respect to the longitudinal axis of the pull rod, an intermediate recess between the forward recess and the rear recess, an elongated indentation extending between the intermediate and rear recesses, the elongated indentation having a substantially planar guide surface.
(c1) providing a cutting head having a forward cutting portion and a rear coupling portion, the rear coupling portion being generally cylindrical in shape and having a longitudinal axis and a recess having a generally axially extending planar coupling surface transversely directed with respect to the longitudinal axis.
(d1) inserting a spring in the elongated hole;
(e1) inserting the pull rod into the elongated hole, with the guide surface horizontal and facing towards the second threaded bore, until the rear end of the pull rod engages the spring;
(f1) inserting the securing screw partially into the threaded securing screw bore; and
(g1) inserting and completely tightening the guide screw in the second threaded bore;
the final assembling procedure comprising the steps of:
(a2) positioning the cutting head adjacent the front end of the pull rod so that the rear coupling portion of the cutting head cooperates with the forward coupling portion of the pull rod, with the coupling surface of the cutting head abutting the coupling surface of the pull rod, the forward coupling portion of the pull rod and the rear coupling portion of the cutting head forming a joint coupling region;
(b2) urging the pull rod rearwardly into the elongated hole, whilst maintaining the rear coupling portion of the cutting head in cooperation with the forward coupling portion of the pull rod, until the rear recess of the pull rod is adjacent the threaded securing screw bore; and
(c2) screwing the securing screw into the threaded securing screw bore so that a forward portion of the securing screw enters the rear recess of the pull rod and urges the pull rod axially rearwardly further into the elongated bore until the rear coupling portion of the cutting head is securely located in the first cylindrical bore, whereby the joint coupling region is retained in the forward portion of the elongated hole.